Question

Compare and contrast the structures of the following solids. a. diamond versus graphite b. silica versus silicates versus glass

Short answer

Diamond and graphite are both allotropes of carbon with different structures leading to distinct properties. Diamond has a three-dimensional lattice structure with tetrahedral bonding, resulting in hardness, a high melting point, and excellent thermal conductivity. Graphite has a planar, layered structure with hexagonal rings, resulting in good electrical conductivity and lubricating properties. Silica, silicates, and glass are silicon-based compounds with varying structures. Silica is a crystalline, covalent network structure, while glass is amorphous. Both have SiO4 tetrahedra in their structure, but silicates have diverse structures due to other elements. Glass is formed by rapidly cooling a silica-based liquid, resulting in a random arrangement, transparency, and brittleness.

Step-by-step solution

Comparing Diamond and Graphite

Diamond and graphite are both allotropes of carbon, which means they are chemically identical but have different structural arrangements of carbon atoms leading to different properties. Let's break down their structures: 1. Diamond: In a diamond crystal, each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral shape. This strong covalent bonding creates a rigid, three-dimensional lattice structure, giving diamonds their unique properties like extreme hardness, high melting point, and excellent thermal conductivity. 2. Graphite: Graphite has a layered structure where carbon atoms are arranged in planar hexagonal rings. Within each layer, carbon atoms are bonded to three other carbon atoms through strong covalent bonds, and the layers are held together by weak Van der Waals forces. This layered structure gives graphite its unique properties like good electrical conductivity within the layers, lubricating properties, and relative softness. Comparing the structures of diamond and graphite: - Diamond has a three-dimensional lattice structure, while graphite has a planar, layered structure. - Carbon atoms in diamond are tetrahedrally bonded, while in graphite they are bonded in planar hexagonal rings. - Diamond's structure results in extreme hardness, high melting point, and excellent thermal conductivity, while graphite's structure results in good electrical conductivity and lubricating properties.

Comparing Silica, Silicates, and Glass

Silica, silicates, and glass are all silicon-based compounds. However, their structures and bonding vary, as detailed below: 1. Silica (SiO2): Silica, also known as silicon dioxide, is a covalent network solid where each silicon atom is bonded to four oxygen atoms in a tetrahedral arrangement. In turn, each oxygen atom is bonded to two silicon atoms. Silica forms a three-dimensional framework of SiO4 tetrahedra, which creates a stable, rigid structure with a high melting point. 2. Silicates: Silicates are a vast group of minerals composed of silicon, oxygen, and other elements such as aluminum, magnesium, iron, and potassium. They share a basic building unit of SiO4 tetrahedra, similar to silica. However, these tetrahedra can be arranged in different ways and can be linked to other cations, forming diverse structures and a wide range of silicate minerals. 3. Glass: Glass is an amorphous solid, meaning it lacks the long-range order found in crystalline materials like silica and silicates. Glass is formed by rapidly cooling a silica-based liquid, preventing it from forming a regular crystalline lattice. The structure of glass is composed of SiO4 tetrahedra interconnected with other elements such as sodium or calcium, with a random arrangement. This lack of long-range order results in properties like transparency and brittleness. Comparing the structures of silica, silicates, and glass: - Silica forms a crystalline, covalent network structure, while glass is an amorphous solid. - Both silica and silicates have SiO4 tetrahedra in their structure, but silicates can have diverse structures due to the addition of other elements. - Glass is formed by rapidly cooling a silica-based liquid, resulting in a random arrangement and properties like transparency and brittleness.